The disclosure relates to a method for manufacturing a semiconductor device; and, more particularly, to a method for forming a metal line in a semiconductor device.
Generally, metal lines in semiconductor devices are formed by using thin metal films made of Al or Cu, for example. Electrical contacts and pad connections between two semiconductor devices allow circuits formed in a semiconductor substrate to be connected to each other.
Such metal lines may be formed by using a Via-First Dual Damascene process for connecting device electrodes and pads separated by an insulating film such as an oxide layer. The insulating film is selectively etched to form a via hole. A photoresist film is deposited, covering the substrate and filling the via hole. A trench pattern is formed in the insulating film by first exposing and etching the photoresist film. The insulating film is then etched to form a trench by using the trench pattern as a mask. The trench pattern and the filling film are then removed, and the inner portion of the via hole and the inner portion of the trench are filled with a metal film.
When a process like this is used to design a circuit pattern, due to problems related to, for example, the critical dimension or minimum feature size, a photoresist film may be improperly formed. The film should be removed and another photoresist film should be deposited to form another photoresist pattern. Hereinafter, the process of reworking the photoresist pattern as described above will be referred to as a photoresist film rework process.
In a photoresist film rework process, the improperly formed photoresist film is removed. The photoresist film may be removed by a dry etching process or a wet etching process.
However, when an improper trench pattern needs to be removed and a photoresist film rework process is carried out, a particular problem may surface. Not only the improper trench pattern itself but also the thick photoresist layer filling the inner portion of the via hole should be removed.
On a semiconductor substrate in which the trench pattern and the filling film have been removed, residues of the photoresist film may remain through the dry cleaning process and the wet cleaning process. If a photoresist film rework process is then used to form other metal lines and via holes, the residues of the previous photoresist film may cause deformations in the critical dimensions of the vias and lines, thereby degrading the electrical characteristics of the semiconductor devices and reducing the yield of the products.
Moreover, since the photolithography/etching processes are performed twice when the Via-First process is used to form the metal lines, the manufacturing costs for the products may be increased.